This application claims priority from Korean Patent Application No. 2003-7442, filed on Feb. 6, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.
1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a screen and a projection television comprising the screen. More particularly, the present invention relates to a screen having a wide viewing angle and a projection television comprising the screen.
2. Description of the Related Art
With increasing screen sizes of displays, studies about displays providing good image quality regardless of the positions of viewers, i.e., viewing angles have been done.
FIG. 1 is a schematic exploded perspective view of a conventional projection screen. Referring to FIG. 1, a conventional projection screen comprises a Fresnel lens sheet 11 converting light emitted from an image source into parallel light, a horizontal lenticular lens sheet 13 disposed on the front surface of the Fresnel lens sheet 11 and comprising vertical cylindrical lenses 12 arranged in a horizontal direction to emit light in a horizontal direction, and a protective filter 15 transmitting light output from the lenticular lens sheet 13 and protecting the lenticular lens sheet 13. Here, black stripes 14 are positioned on protrusions for connection of the cylindrical lenses 12, which are formed at an exit face of the horizontal lenticular lens sheet 13. The black stripes serve to absorb light output from the protrusions and to block external light, thereby increasing a contrast ratio.
A conventional projection screen can provide a wide horizontal viewing angle. However, a relatively narrow vertical viewing angle is provided.
FIG. 2 is a graph showing the intensity of light finally output from the conventional projection screen shown in FIG. 1 according to a viewing angle of a viewer. Here, f0 represents light distribution according to a horizontal viewing angle in the absence of a lenticular lens sheet, f1 represents light distribution according to a vertical viewing angle in the presence of a lenticular lens sheet, and f2 represents light distribution according to a horizontal viewing angle in the presence of a lenticular lens sheet. Referring to FIG. 2, with respect to a viewing angle distribution having light intensity corresponding to a half of the maximal light intensity, f0 has a standard viewing angle distribution θO, f2 has a wide horizontal viewing angle distribution θH, and f1 has a narrow vertical viewing angle distribution θV.
Conventionally, in order to increase a vertical viewing angle, a light-diffusing agent is incorporated into a lenticular lens sheet. Alternatively, a vertical lenticular lens sheet having a vertical array of horizontal cylindrical lenses can be further used, like in a rear projection screen disclosed in Korean Patent Laid-Open Publication No. 2000-15228.
However, since the light-diffusing agent is used in a large amount, using the light-diffusing agent increases diffusion of light, thereby increasing loss of light amount. On the other hand, using the vertical lenticular lens sheet can slightly increase a vertical viewing angle. However, while light passes through two lenticular lens sheets, loss of light increases due to reflection or diffusion, thereby lowering brightness and contrast ratio. In addition, conventionally, a vertical lenticular lens sheet is formed on a surface of a Fresnel lens sheet or is separately formed, thereby increasing burdens on processing.